Regioselective addition of Grignard reagents to N-acylpyrazinium salts: synthesis of substituted 1,2-dihydropyrazines and Δ⁵-2-oxopiperazines

• Valentine R. St. Hilaire,
• William E. Hopkins,
• Yenteeo S. Miller,
• Srinivasa R. Dandepally and
• Alfred L. Williams

Beilstein J. Org. Chem. 2019, 15, 72–78, doi:10.3762/bjoc.15.8

• recently showed that 3-alkoxy-substituted N-acylpyrazinium salts can be selectively reduced by tributyltin hydride to afford 1,2-dihydropyrazines in good to excellent yields [9]. There have been other reports involving the addition of TMS-ketene acetals to pyrazinium salts [10][11][12]. A double

• either an ethyl or benzyl group on the pyrazinium salts gave an 81% yield for both 10 and 11 (Figure 1). Reacting a Grignard with pyrazinium salts disubstituted with electron-donating alkoxy groups gave us the desired dihydropyrazine in moderate to good yields of 45–88% (Figure 1, compounds 8, 9a,b

Cobalt- and rhodium-catalyzed carboxylation using carbon dioxide as the C1 source

• Tetsuaki Fujihara and
• Yasushi Tsuji

Beilstein J. Org. Chem. 2018, 14, 2435–2460, doi:10.3762/bjoc.14.221

• scope was examined (Scheme 11). Allylbenzene was converted into its corresponding carboxylated product 12a in an isolated 68% yield, and various functionalized allylarenes bearing trifluoromethyl (11b) and alkoxy (11c,d) substituents were tolerated. The selectivity of the reaction was demonstrated with

Cationic cobalt-catalyzed [1,3]-rearrangement of N-alkoxycarbonyloxyanilines

• Itaru Nakamura,
• Mao Owada,
• Takeru Jo and
• Masahiro Terada

Beilstein J. Org. Chem. 2018, 14, 1972–1979, doi:10.3762/bjoc.14.172

• promoted the [1,3]-alkoxy rearrangement of N-alkoxyaniline [15], the cationic NHC-Cu catalyst generated from IPrCuBr and AgSbF6 was totally inefficient for the present reaction; 1a was decomposed under the reaction conditions (Table 1, entry 19). Whereas AgSbF6 promoted the reaction at 60 °C (Table 1

Design, synthesis and structure of novel G-2 melamine-based dendrimers incorporating 4-(n-octyloxy)aniline as a peripheral unit

• Cristina Morar,
• Pedro Lameiras,
• Attila Bende,
• Gabriel Katona,
• Emese Gál and
• Mircea Darabantu

Beilstein J. Org. Chem. 2018, 14, 1704–1722, doi:10.3762/bjoc.14.145

• (ethynyl)-s-triazine and various icosanyloxyphenylazides) with liquid crystalline and luminescent properties [22]. On the other hand, mesogenic supramolecular perylene bisimide assemblies with a number of 2-amino-4,6-bis[(4-alkoxy)phenylamino]-s-triazines [23], amphiphilic azobenzene-containing linear

• (in B) and rigid 1,4-phenylene with adjustable alkoxy-spacers (n = 1, 3, in C1 and C3, respectively). G-1 chloro- and piperazine-dendrons, D-Cl and D-N

  NH, as well as central building blocks B, C1 and C3, had s-triazine rings linked by C(s-triazine)–N(exocyclic) partial double bonds, which exist due

β-Hydroxy sulfides and their syntheses

• Mokgethwa B. Marakalala,
• Edwin M. Mmutlane and
• Henok H. Kinfe

Beilstein J. Org. Chem. 2018, 14, 1668–1692, doi:10.3762/bjoc.14.143

• (-CH2X), alkoxy (-CH2O), aryloxy (PhO), aryl (Ph) and alkyl (-CH2) substituents on the epoxide. The virtues of this protocol are the low cost and ready availability of NBS, its moisture and air stability as well as low toxicity. The reaction is characterized by short reaction time, good to high product

• alkene to form radical 87. This intermediate undergoes oxidation followed by decomposition to provide the alkoxy radical intermediate 88, which then affords the β-hydroxy sulfide 81 upon protonation. The considerably stronger S–S bonds of the dialkyl disulfides and the lower stability of the expected

Glycosylation reactions mediated by hypervalent iodine: application to the synthesis of nucleosides and carbohydrates

• Yuichi Yoshimura,
• Hideaki Wakamatsu,
• Yoshihiro Natori,
• Yukako Saito and
• Noriaki Minakawa

Beilstein J. Org. Chem. 2018, 14, 1595–1618, doi:10.3762/bjoc.14.137

• , similar deformylation by action of hypervalent iodine has also been demonstrated: the β-fragmentation reaction of an anomeric alkoxy radical of carbohydrates was mediated by a hypervalent iodine reagent [73]. The reaction results in the formation of carbohydrates with a reduction of one carbon. From the

• viewpoint of the synthetic method, the reaction would be useful for dehomologation of aldoses and preparation of chiral synthons deriving from sugars. The reaction procedure involves the initial formation of an alkoxy anomeric radical by a hypervalent iodine reagent in the presence of iodine, which triggers

One hundred years of benzotropone chemistry

• Arif Dastan,
• Haydar Kilic and
• Nurullah Saracoglu

Beilstein J. Org. Chem. 2018, 14, 1120–1180, doi:10.3762/bjoc.14.98

Phosphodiester models for cleavage of nucleic acids

• Satu Mikkola,
• Tuomas Lönnberg and
• Harri Lönnberg

Beilstein J. Org. Chem. 2018, 14, 803–837, doi:10.3762/bjoc.14.68

Chlorination of phenylallene derivatives with 1-chloro-1,2-benziodoxol-3-one: synthesis of vicinal-dichlorides and chlorodienes

• Zhensheng Zhao and
• Graham K. Murphy

Beilstein J. Org. Chem. 2018, 14, 796–802, doi:10.3762/bjoc.14.67

• -dichlorides. Substrates with α-ethyl (2r) and α-isopropyl (2s) substituents reacted similarly, giving chlorinated products in 63–65% yield. Lastly, vinylidene 2t gave chlorodiene 4t as the sole product in 74% yield. As with alkoxy substrate 2m, the α-methylated substrates 2u and 2v possessing methoxy group(s

Recent developments in the asymmetric Reformatsky-type reaction

• Hélène Pellissier

Beilstein J. Org. Chem. 2018, 14, 325–344, doi:10.3762/bjoc.14.21

• that of sulfinyl imines (S)-25c,d exhibiting an α-benzyloxy substituent provided high diastereoselectivities (76–88% de). This assumed the coordination of the α-alkoxy group to zinc. Even a higher diastereoselectivity of >90% de was achieved for more sterically hindered α-alkoxy-derived substrates (S

5-Aminopyrazole as precursor in design and synthesis of fused pyrazoloazines

• Ranjana Aggarwal and
• Suresh Kumar

Beilstein J. Org. Chem. 2018, 14, 203–242, doi:10.3762/bjoc.14.15

• screened for their cytotoxic activity against human colon carcinoma (Colo-205) cell lines (Scheme 35). Buriol et al. [92] described the reaction of 5-aminopyrazole 16 with 4-alkoxy-1,1,1-trifluoro-3-alken-2-ones 129 to yield pyrazolo[1,5-a]pyrimidine derivatives 130 in acetic acid and ethanol using

• -aminopyrazole derivatives 16/126 with β,γ-unsaturated-γ-alkoxy-α-ketoesters 175 for the regioselective synthesis of pyrazolo[1,5-a]pyrimidines 177 in refluxing ethanol. The reaction provided high regioselectivity compared to other 1,3-dielectrophiles like 1,3-dicarbonyl compounds. The reaction was proposed to

Progress in copper-catalyzed trifluoromethylation

• Guan-bao Li,
• Chao Zhang,
• Chun Song and
• Yu-dao Ma

Beilstein J. Org. Chem. 2018, 14, 155–181, doi:10.3762/bjoc.14.11

• corresponding products in moderate to good yields. This reaction can tolerate a variety of functionalities, such as alkoxy, amino, ester, and nitro groups. However, a reaction temperature up to 100 °C and the requirement of excessive TMSCF3 (bp 55 °C) rendered the former reaction less than ideal. In 2012, the

• groups. This reaction can tolerate a variety of functionalities, such as alkoxy, amino and halide groups. The author proposed a plausible mechanism depicted in Scheme 42. At first, a dinitrogen ligated complex (N,N)CuX A is generated in situ by the reaction of CuI with phen. Then, a copper(I)-acetylide

CF₃SO₂X (X = Na, Cl) as reagents for trifluoromethylation, trifluoromethylsulfenyl-, -sulfinyl- and -sulfonylation. Part 1: Use of CF₃SO₂Na

• Hélène Guyon,
• Hélène Chachignon and
• Dominique Cahard

Beilstein J. Org. Chem. 2017, 13, 2764–2799, doi:10.3762/bjoc.13.272

• excellent yields. However, to achieve high yields in this trifluoromethylation, one (or more) alkoxy group(s) must be present on the arenes in order to stabilise the free-radical intermediate (see mechanism in Scheme 47). Control experiments such as the trapping of the trifluoromethyl radical with the

Hydrolysis, polarity, and conformational impact of C-terminal partially fluorinated ethyl esters in peptide models

• Vladimir Kubyshkin and
• Nediljko Budisa

Beilstein J. Org. Chem. 2017, 13, 2442–2457, doi:10.3762/bjoc.13.241

• fragments decreases. The partially fluorinated ethoxy moieties reported here represent an intermediate situation between the partially fluorinated methoxy and propoxy/higher alkoxy groups (logP: CF3 > CHF2 ≈ CH3 > CH2F). Amide isomerism The tertiary amide bond in N-acylprolyl can exist in two conformational

• dielectric constant, as would be expected from an electrostatic interaction between the polar alkoxy group and the amide moiety (Figure 4). A somewhat similar situation has been recently reported by Siebler et al. for the C-terminal amide in dimethylamido N-acetylproline, where the conformational equilibrium

• function as an intramolecular probe of the C-terminal ester group polarity. Notably, the predicted flexibility of the partially fluorinated alkoxy groups in the presence of other strong dipoles is inconsistent with the concept of conformational adaptors elaborated by Müller et al. quite recently [44][65

Electron-deficient pyridinium salts/thiourea cooperative catalyzed O-glycosylation via activation of O-glycosyl trichloroacetimidate donors

• Mukta Shaw,
• Yogesh Kumar,
• Rima Thakur and
• Amit Kumar

Beilstein J. Org. Chem. 2017, 13, 2385–2395, doi:10.3762/bjoc.13.236

• presence of Schreiner′s thiourea in the reaction medium enhances the acidity of the ammonium salt due to doubling their dual hydrogen bonding ability with the carboxylate and the alkoxy group of the ammonium salt. A thiourea derivative also enhances the nucleophilicity of the glycosyl acceptor by imparting

• by the introduction of a cocatalyst such as an aryl thiourea derivative, which has the ability to form a dual hydrogen bond with the carboxylate and the alkoxy group of the ammonium salt [42][43][44]. To ensure our postulation, a 1H NMR spectroscopic study was carried out with a mixture of glycosyl

Structure–property relationships and third-order nonlinearities in diketopyrrolopyrrole based D–π–A–π–D molecules

• Jan Podlesný,
• Lenka Dokládalová,
• Oldřich Pytela,
• Adam Urbanec,
• Milan Klikar,
• Numan Almonasy,
• Tomáš Mikysek,
• Jaroslav Jedryka,
• Iwan V. Kityk and
• Filip Bureš

Beilstein J. Org. Chem. 2017, 13, 2374–2384, doi:10.3762/bjoc.13.235

• -photon absorbers (2PA). In this respect, the central DPP bicyclic lactam is often decorated with electron donors such as alkoxy- or dialkylamino groups [11][12], triphenylamine [13][14], heterocyclic carbazole [15], thiophene [16][17], furan [18], and organometallic ferrocene [19]. 2PA-active DPPs were

Synthesis and application of trifluoroethoxy-substituted phthalocyanines and subphthalocyanines

• Satoru Mori and
• Norio Shibata

Beilstein J. Org. Chem. 2017, 13, 2273–2296, doi:10.3762/bjoc.13.224

• organic solvents is extremely high. Therefore, TFEO-Pcs can be easily purified by silica gel column chromatography. In addition, when a phthalocyanine is substituted with an electron-donating group, such as an alkoxy group, the electron density in the phthalocyanine macrocycle increases, making it easily

• iron phthalocyanine (TFEO-FePc) were compared with non-fluorinated alkoxy-substituted phthalocyanines [52]. A slightly bathochromic shift of the Q band was observed for TFEO-Pcs relative to non-fluorinated alkoxylated phthalocyanines. Although the melting points of non-fluorinated alkoxylated

• phthalocyanines are lower than 200 °C, TFEO-NiPc does not melt below 300 °C. Phthalocyanine iron complexes, which are substituted by non-fluorinated alkoxy groups at all peripheries, are easily oxidized and unstable, so these cannot even be synthesized. On the other hand, TFEO-FePc is stabilized by the strong

Conjugated nitrosoalkenes as Michael acceptors in carbon–carbon bond forming reactions: a review and perspective

• Yaroslav D. Boyko,
• Valentin S. Dorokhov,
• Alexey Yu. Sukhorukov and
• Sema L. Ioffe

Beilstein J. Org. Chem. 2017, 13, 2214–2234, doi:10.3762/bjoc.13.220

• of Michael addition to acyclic nitrosoalkenes NSA4. Stereochemistry of Michael addition to γ-alkoxy nitrosoalkene NSA5. Oppolzer’s total synthesis of 3-methoxy-9β-estra(1,3,5(10))trien(11,17)dione (25). Oppolzer’s total synthesis of (+/−)-isocomene. Weinreb’s total synthesis of alstilobanines A, E

A novel approach to oxoisoaporphine alkaloids via regioselective metalation of alkoxy isoquinolines

• Benedikt C. Melzer and
• Franz Bracher

Beilstein J. Org. Chem. 2017, 13, 1564–1571, doi:10.3762/bjoc.13.156

• Benedikt C. Melzer Franz Bracher Department für Pharmazie - Zentrum für Pharmaforschung, Ludwig-Maximilians Universität München, Butenandtstr. 5-13, D-81377 Munich, Germany 10.3762/bjoc.13.156 Abstract Oxoisoaporphine alkaloids are conveniently prepared via direct ring metalation of alkoxy

• synthesis of oxoisoaporphines. By using our modification (1.5 equivalents of TMPMgCl∙LiCl over 4 h at room temperature) [13] of Knochel’s [23] protocol for the metalation of isoquinolines, the alkoxy-substituted isoquinolines 7a,b were metalated at C-1, as shown before, and this method could conveniently be

• direct ring metalation of alkoxy isoquinolines at C-1, followed by the reaction with iodine as central step. Subsequent Suzuki cross-coupling to methyl 2-(isoquinolin-1-yl)benzoates and intramolecular acylation with Eaton’s reagent afforded five alkaloids of the oxoisoaporphine type. Significant

1-Imidoalkylphosphonium salts with modulated C_α–P⁺ bond strength: synthesis and application as new active α-imidoalkylating agents

• Jakub Adamek,
• Roman Mazurkiewicz,
• Anna Węgrzyk and
• Karol Erfurt

Beilstein J. Org. Chem. 2017, 13, 1446–1455, doi:10.3762/bjoc.13.142

• difficult and elaborate. Most of these, including the most frequently used α-alkoxy derivatives (Z = OR), N-[1-(benzotriazol-1-yl)alkyl]amides (Z = 1-benzotriazolyl) and 1-(N-acylamino)alkyl sulfones (Z = SO2Ar) require activation with Lewis acids, which are expensive (e.g., ZrCl4, VCl3, CeCl3, Bi(OTf)3 or

• aromatic systems with strong electron-donating substituents (e.g., alkoxy-, polyalkoxy- and aminoarenes), or some activated heterocyclic systems such as indole [3][8][10][24][25]. The α-imidoalkylation reaction using N-(1-hydroxyalkyl)imides (almost entirely N-hydroxymethylphthalimide) in sulfuric acid

Synthesis of 1-indanones with a broad range of biological activity

• Marika Turek,
• Dorota Szczęsna,
• Marek Koprowski and
• Piotr Bałczewski

Beilstein J. Org. Chem. 2017, 13, 451–494, doi:10.3762/bjoc.13.48

• to a mixture of 1,2-dihydroisoquinolines 236 and substituted 1-indanone derivatives 237 via alkoxy group migration in 16 and 57% yields, respectively (Scheme 66) [95]. 2 Construction of the 6-membered ring The titles of subsections in this chapter contain names of the 1-indanone precursors which

Iodination of carbohydrate-derived 1,2-oxazines to enantiopure 5-iodo-3,6-dihydro-2H-1,2-oxazines and subsequent palladium-catalyzed cross-coupling reactions

• Michal Medvecký,
• Igor Linder,
• Luise Schefzig,
• Hans-Ulrich Reissig and
• Reinhold Zimmer

Beilstein J. Org. Chem. 2016, 12, 2898–2905, doi:10.3762/bjoc.12.289

• -alkoxy-γ-amino-aldehydes and ketones [14]. In this context, a series of publications of our group reported on syntheses of carbohydrate mimetics [15][16][17][18][19][20] that are based on aminopyrans, aminooxepanes or other aminopolyols and that were examined for example as ligands of L- and P-selectin

• ], although the direct β-iodination of enol ethers using a suitable electrophilic iodine reagent is relatively underdeveloped. For the iodination of 4-alkoxy-3,6-dihydro-1,2-oxazines 3, we selected molecular iodine as the most simple iodination reagent in the presence of a base [28][29][30]. A clean reaction

Symmetry-based approach to oligostilbenoids: Rapid entry to viniferifuran, shoreaphenol, malibatol A, and diptoindonesin G

• Youngeun Jung,
• Dileep Kumar Singh and
• Ikyon Kim

Beilstein J. Org. Chem. 2016, 12, 2689–2693, doi:10.3762/bjoc.12.266

• natural oligostilbenoids guided us to design a modular synthetic approach to these molecules by utilizing a three-step sequence consisting of Sonogashira coupling, iodocyclization, and Suzuki coupling. During our synthesis, the relative reactivities of ester, aldehyde, and alkoxy groups on the same aryl

• , 2, and 3) were readily available from the corresponding C2 symmetric precursors via monoiodination, we decided to evaluate this route. In particular, we wondered what functional group as a G moiety would be appropriate for the successful iodine-mediated cyclization. Ester, aldehyde, and alkoxy

• product which decomposed eventually. On the other hand, 6 was successfully converted to the desired 3-iodobenzofuran 11 in good yield. These results led us conclude that either ester or aldehyde groups perform as better nucleophiles than an alkoxy group in the iodocyclization. Having secured gram

Amidofluorene-appended lower rim 1,3-diconjugate of calix[4]arene: synthesis, characterization and highly selective sensor for Cu²⁺

• Rahman Hosseinzadeh,
• Mohammad Nemati,
• Reza Zadmard and
• Maryam Mohadjerani

Beilstein J. Org. Chem. 2016, 12, 1749–1757, doi:10.3762/bjoc.12.163

• ]arene bearing anthraceneisoxazolymethyl [3], quinolone [28], 5-nitrosalicylaldehyde [29], 3-alkoxy-2-naphthoic acid [30], coumarine [31] and benzothiazole [10][15] groups. In continuation of our studies on developing novel chemosensors containing fluorenyl moieties as fluorogenic group [32][33][34], we

Rearrangements of organic peroxides and related processes

• Ivan A. Yaremenko,
• Vera A. Vil’,
• Dmitry V. Demchuk and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2016, 12, 1647–1748, doi:10.3762/bjoc.12.162

• a good leaving group. The Criegee rearrangement was discovered in 1944 in the reaction of decaline ethylperoxoate 127 that rearranged into isomeric ester ketal 128 (Scheme 39) [291]. The mechanism of the Criegee rearrangement was studied using 2-alkoxy-2-propyl per-4-nitrobenzoates [292]. It was

• -oxabicycloalkanes 147a–d in formic or acetic acid containing catalytic amounts of sulfuric acid affords ω-alkoxy-(ω-3)-hydroxyalkanoic acid lactones 148a–d and 149a–d (Table 10) [297]. The transformation of 1-hydroperoxy-2-oxabicycloalkanones 147a–d into ω-alkoxy-(ω-3)-hydroxyalkanoic acid lactones 148a–d and 149a